Acta Tropica 34 1 53 60 SWITZERLAND

Studies in mice infected with T. brucei or T. congolense showed that increased red cell destruction in the spleen occurred as from the third day of patent parasitaemia and this resulted in a marked reduction of the half-life of transfused syngeneic 51Cr labelled cells. There was a progressive increase in the osmotic fragility of the red cells, especially in T. congolense infected mice which also showed a more severe anaemia. The antiglobulin test was only rarely positive in the late stages of T. brucei infection. Incubation of normal red cells with plasma from infected mice in vitro did not result in haemolysis, but in the case of plasma from T. brucei infected mice, it caused an appreciable reduction in the half-life of the cells when transfused into normal mice. It is suggested that mechanisms of red cell destruction in trypanosome infections are complex and may vary with the species of trypanosomes, the host and the stage of infection